This invention relates generally to the art of dental restorations and more particularly to a novel ceramic material for incorporating into a dental composite and a process of producing such material.
Conventionally, human teeth have been treated for decay in dental processes wherein the decayed material is removed by a grinding process and replaced with a material which is generally compatible with the outside enamel and generally nonreactive with the dentine material therebelow. Such material has normally been in the form of an alloy of silver mixed with mercury and referred to as dental amalgam.
Dentists and dental technicians for years have become accustomed to working with such amalgam and have developed the ability to restructure and reshape a tooth surface due to the ability of such amalgam material to respond to molding utilizing dental tools. Such molding is referred to as condensibility and is largely related to the ability of such material to respond to forces applied in directions other than the direction of the applied force. This permits the application of a downward pressure of a dental tool to cause such material to respond laterally and conform to a lateral mold. During the condensation process mercury is forced from the amalgam and removed by mopping such that the mercury content of the amalgam content is actually reduced.
Such dental amalgam, however, has shortcomings with regard to both the cosmetic appearance and durability.
In recent years, a variety of ceramic filled polymer materials have become available which are compatible with the human tooth structure and which may be formed into composites possessing high durability. These materials possess ability to be produced in desired colors. Examples of such polymeric materials are set forth in U.S. Pat. No. 4,744,759 to Bowen which is herein incorporated by reference. The Bowen patent describes not only polymers for use in dental restorations but also a composite material for use in such restoration.
Composite materials involving the use of polymers have been found in general to suffer from the disadvantage of the lack of a formability of the type normally exercised by a dentist during dental restoration. This is generally a lack of the property referred to as condensibility for conventional amalgams. Many composites also have not possessed the wear resistance of conventional amalgams.
Ehrnford in U.S. Pat. Nos. 4,381,918 and 4,392,828 describes processes of producing a material useful in a dental composite utilizing bonded glass fiber matrices. Such fiber matrices have been found to generally possess the characteristics of condensibility required for forming a dental restoration in the conventional manner. The fiber matrix also provided also enhanced wear resistance.
A shortcoming, however, of such glass fiber matrices is the expense thereof associated with very close tolerances required in the manufacturing process.